Java EE (Java Enterprise Edition) General Discussion

I know there are numerous threads on this, but none seem to have any solutions. Here's my problem (and setup):

I have jsps and servlets in a web application. I have setup IIS and Tomcat, so that any jsp files that are sent to IIS are forwarded to tomcat, processed, and passed back to IIS and then to the end user. A user can acces the jsp files via http://<server ip address>/<filename>.jsp (i.e. doesn't need port 8080 stated)

I want to get the username of the remote user accessing the jsp page. In so many threads people say "just call getRemoteUser() function", but it is returning null. I've allowed port 80 to be open. I've tried to set up automatic windows authentication (clicked the checkbox in IIS). But still, upon getting to the website a dialog box pops up and even when user information is entered correctly the value is null.

Question: How do i stop the need for the dialog boxes to pop up?
Question: Can a webapp get the logged in remote user's details using just IE, WinXP, tomcat and IIS?
Question: How do I ensure a user is correctly authenticated? How do I authenticate users?

I have been trying to solve this problem for about a fortnight now, and it seems impossible.

Thanks for reading

Ed